Alternator quit charging right after cluster swap - Ideas?

[Greentoy]

4 minutes ago, Ωhm said:

 

Probably too late for a photo. But for myself, lesson learned here.

I didn't think to take a photo of the back of the cluster.  I should have.  We are always learning, as long as we are willing to learn I suppose.

[Greentoy]

7 minutes ago, eaglescout526 said:

Dang. What a hassle to just find that out. Glad it’s working again! 

Yeah, I was starting to get a bit frustrated this week. Now I can move forward with other stuff.  :)

[CGCWO]

I’ll have to look into this when my new Alt arrives later this week. Thanks again for all of the knowledge!

[CGCWO]

On 1/21/2021 at 8:20 PM, Greentoy said:

This is the part you need on the yellow wire.  You will need to cut out the yellow wire, crimp the side that has the black connector to the tan wire and the other side to an ignition 12v circuit ( I used the diagnostic link input wire) 

So I wasn’t an EM or ET was BM and struggle with wiring. I just did the cluster swap on my 1987 4.0 and have run into the same problem.  I am going to PM you regarding your fix.

[CGCWO]

Followed @Greentoy s directions and now I have a charging alternator! One difference I had is no yellow wire to small diagnostic block. I used the red wire instead. 
 

*Correction: on the 87 4.0 Renix use the orange wire, Again use the orange wire. I came out to a dead battery after the truck sitting for a couple of days after I used the red wire. 

[gvthnks]

On 1/21/2021 at 9:10 PM, Greentoy said:

  The tan wire does NOT dead end at the cluster as the diagrams show.  Rather than disassembling the cluster which can be done without that much trouble, I opted to install a new diode inline between the tan wire in the harness and the ignition feed that runs in to the diagnostic connector under the hood since they are right next to each other.  I ran down to the parts store and picked up a Standard connector adapter(part #S792) to use the diode from it (old chevy style).  Crimped and shrink wrapped all connections, and now the alternator charges fine. I think I'll just keep the new alternator installed and keep my old one as a backup.  Now that we are charging again, I can resume my cruise install and move on to the A/C system before spring.  

 

On 1/21/2021 at 9:20 PM, Greentoy said:

This is the part you need on the yellow wire.  You will need to cut out the yellow wire, crimp the side that has the black connector to the tan wire and the other side to an ignition 12v circuit ( I used the diagnostic link input wire) 

 

Can you elaborate on this?  

Which way is the diode oriented in the harness pictured?  If I read it correctly, then the yellow wire AND the red wire (both small wires going to the alternator) need power on them to excite and make the alternator charge?  What is the value of that diode?  I tried to look up the part number you shared, but come up with nothing.  

 

Thanks

[Bobbie]

On 1/21/2021 at 8:20 PM, Greentoy said:

This is the part you need on the yellow wire.  You will need to cut out the yellow wire, crimp the side that has the black connector to the tan wire and the other side to an ignition 12v circuit ( I used the diagnostic link input wire) 

 

[Bobbie]

On 4/7/2021 at 9:53 PM, CGCWO said:

So I wasn’t an EM or ET was BM and struggle with wiring. I just did the cluster swap on my 1987 4.0 and have run into the same problem.  I am going to PM you regarding your fix.

I ran mine for a bit after the swap and it did fine, altinator went bad and replaced with new and cannot get it to charge unless wipers are on, or unplug harness? What size diode would It need to replace the one in cluster?